1. Field of the Invention
The present general inventive concept relates to an electrophotographic image forming apparatus, and more particularly, to a structure to maintain steady rotation speed of an optical photoconductor in an electrophotographic image forming apparatus.
2. Description of the Related Art
Generally, an electrophotographic image forming apparatus supplies a developer, i.e., a toner, to an electrostatic latent image, which is formed on a surface of an optical photoconductor using an optical scan, to convert the electrostatic latent image into a toner image and transfers and fuses the toner image onto a print medium, thereby printing a desired image.
The optical photoconductor on which the electrostatic latent image is formed needs to maintain steady rotation in accordance with a speed at which a print medium such as a paper is fed. When the rotation speed of the optical photoconductor changes due to a temporal disturbance, deterioration of print quality, referred to as “jitter” may occur in an image printed onto the paper. In the meantime, when the optical photoconductor and a developer roller, which supplies the toner to the optical photoconductor, are rotated by a rotation device other than a gear, which couples the optical photoconductor and the developer roller, such as drive shafts, to which the optical photoconductor and the developer roller are separately connected within the electrophotographic image forming apparatus, a linear velocity of an outer circumference of the developer roller is typically about 1.2 times greater than that of the optical photoconductor in order to efficiently supply the toner to the optical photoconductor. Due to such difference in linear velocity, a torque is applied to the optical photoconductor which is in contact with the developer roller, and thus the rotation speed of the optical photoconductor may be increased.
To prevent such change in a rotation speed of an optical photoconductor, structures for maintaining a steady rotation speed of an optical photoconductor have been published. FIG. 1 is a cross-section of an example of a conventional structure for maintaining a steady rotation speed of an optical photoconductor in an electrophotographic image forming apparatus.
Referring to FIG. 1, the conventional structure for maintaining a steady rotation speed of an optical photoconductor includes a frame 11 within an image forming apparatus, a optical photoconductor 20, and a damping device 30. The optical photoconductor 20 is connected to the frame 11 via a rotation shaft 23 to be capable of rotating. The damping device 30 includes a pressure member 31 which is pierced by the rotation shaft 23 and whose surface facing a flange 21 installed at an end portion of the optical photoconductor 20 a friction pad 32 is attached to, and a coil spring 33 which is pierced by the rotation shaft 23 and elastically presses the pressure member 31 toward the flange 21 at the end portion of the optical photoconductor 20.
The conventional structure shown in FIG. 1 has a problem in that the coil spring 33 applies a reaction force to the frame 11 and thus deforms the frame 11. In addition, bonding the pressure member 31 and the friction pad 32, which are made of different materials, increases manufacturing costs.
Besides the conventional structure shown in FIG. 1, another conventional structure using a torsion spring installed at a rotation shaft of an optical photoconductor to maintain a steady rotation of the optical photoconductor has been provided. However, the effect of the torsion spring is not satisfactory since the torsion spring does not immediately respond to a torque applied to the optical photoconductor due to an external load.